Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing

TLDR

Irregular sleep schedules have not been systematically examined for their impact on circadian timing and academic performance. The study followed 61 undergraduates for 30 days, recording sleep diaries and calculating a novel sleep regularity index (SRI). Participants were grouped into most and least regular quintiles, and circadian phase and light exposure were measured via salivary dim‑light melatonin onset and wrist photometry, while a mathematical model linked light patterns to circadian timing differences. Irregular sleepers exhibited later DLMO, delayed sleep propensity peaks, reduced light rhythm amplitude, and a positive correlation between SRI and academic performance, indicating that irregular sleep and light exposure are associated with delayed circadian rhythms and lower grades, and that light‑based interventions could improve sleep regularity.

Abstract

The association of irregular sleep schedules with circadian timing and academic performance has not been systematically examined. We studied 61 undergraduates for 30 days using sleep diaries, and quantified sleep regularity using a novel metric, the sleep regularity index (SRI). In the most and least regular quintiles, circadian phase and light exposure were assessed using salivary dim-light melatonin onset (DLMO) and wrist-worn photometry, respectively. DLMO occurred later (00:08 ± 1:54 vs. 21:32 ± 1:48; p < 0.003); the daily sleep propensity rhythm peaked later (06:33 ± 0:19 vs. 04:45 ± 0:11; p < 0.005); and light rhythms had lower amplitude (102 ± 19 lux vs. 179 ± 29 lux; p < 0.005) in Irregular compared to Regular sleepers. A mathematical model of the circadian pacemaker and its response to light was used to demonstrate that Irregular vs. Regular group differences in circadian timing were likely primarily due to their different patterns of light exposure. A positive correlation (r = 0.37; p < 0.004) between academic performance and SRI was observed. These findings show that irregular sleep and light exposure patterns in college students are associated with delayed circadian rhythms and lower academic performance. Moreover, the modeling results reveal that light-based interventions may be therapeutically effective in improving sleep regularity in this population.